The present invention relates generally to display systems, and, more particularly, to a method and system for compensating for defects in a multi-light valve display.
Display systems are used in many applications including graphics applications, video projectors, etc. These display systems typically use an integrated light valve to supply a number of colors, typically red, green and blue, to a display device that includes an array of display pixels. The color of each display pixel is determined by the logic that drives the light valve with the result that a coherent picture is displayed on the display device. A light valve may be visualized as an array of pixels.
When using a single light valve to project white light, xe2x80x9cstuckxe2x80x9d pixels create permanently black or white spots on the projected image. A stuck pixel refers to a defective pixel that is frozen either in the on state or the off state. A pixel that is stuck in its off state appears black, while a pixel that is stuck in its on state appears at the illumination color at full intensity. When a light valve is illuminated with a color, for example red, a pixel stuck on will appear full intensity of the illuminating color (i.e., red) and a pixel stuck off will appear black. At current fabrication yields, it is typical for displays to have one or more stuck pixels.
To achieve a full-color display with a single light-valve, it is common to use a sequential color technique in which three separate images are displayed for each full-color frame: one for red, blue, and green sub-images. However, when a sequential display is used to project a large image, the quick xe2x80x9csaccadicxe2x80x9d, or sporadic, motions of the eye can cause the viewer to see color banding artifacts. This effect results from the color fields being mis-aligned on the moving retina.
To eliminate these sequential color artifacts, it is common for large displays to use multiple light-valves. If red, green and blue images are simultaneously projected from three different light-valves, color artifacts caused by rapid eye movements will be substantially eliminated. The following Table 1 illustrates the timing schedule that a conventional multi-light valve display would follow.
In such a system, light from each pixel of the light valve is used to illuminate a corresponding pixel of the display, so that each display pixel receives light from a corresponding pixel in each light valve.
Unfortunately, in such a system, a defect in any one pixel on a particular light valve will degrade the color gamut available at the display pixel corresponding to the failed light valve pixel. This causes a color shift in the display pixel. For example, a failed-off pixel in light valve 1, the red light valve, will limit the color of the corresponding display pixel to lie somewhere between green and blue, and will prevent the corresponding display pixel from displaying any red component.
Therefore, it would be desirable to have a multi-light valve display that allows compensation for a failed pixel in one or more of the light valves.
The invention provides a method and system for compensating for defects in a multi-light valve display.
The present invention may be conceptualized as a method for operating a display including light valves, each light valve including pixels. The method comprises the steps of controlling, during a time period, light of a first color by a first light valve and light of a second color by a second light valve in the display; and shifting, in a subsequent time period, the light of the first color and the light of the second color such that the light of the second color is controlled by the first light valve and the light of the first color is controlled by the second light valve.
In architecture, the invention is a system for operating a display including light valves, each light valve including pixels. The system comprises a first light source for supplying a light of a first color, a second light source for supplying a light of a second color, a first light valve and a second light valve. The system also includes an illumination schedule that defines the illumination of the light valves so that, during a time period, the light of the first color illuminates the first light valve and the light of the second color illuminates the second light valve. In a subsequent time period, the light of the first color and the light of said second color are shifted such that the light of the second color illuminates the first light valve and the light of the first color illuminates the second light valve.
The invention has numerous advantages, a few of which are delineated, hereafter, as merely examples.
An advantage of the invention is that it reduces or eliminates eye motion artifacts in a display.
Another advantage of the invention is that it reduces the chromatic error caused by a failed pixel in a light valve array.
Another advantage of the invention is that it allows a user of the display to identify to the display logic the location of a defective pixel.
Another advantage of the invention is that it allows the display logic to compensate for a defective pixel in one or more light valves.
Other features and advantages of the invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. These additional features and advantages are intended to be included herein within the scope of the present invention.